This invention relates to a fuel injection system for internal combustion engines, particularly to improvements therein.
It is well known that an electrically operated injection apparatus is used as an injecting device which is supplied with fuel for an interval combustion engines. In conventional fuel injection wherein the nozzle opening time of the fuel injection apparatus is determined by the load on the engine, the number of engine revolutions per minute and temperature, etc., of the engine, a movable armature of the injection apparatus is pushed by a spring toward the closing position, so that the supply of fuel to the engine is stopped. When a magnetizing current flows into a magnetic coil, the movable armature of the injection apparatus is pulled by an electromagnetic force toward the opening position against the action of the spring, so that the fuel is discharged into the engine. When the magnetizing current is discontinued, the movable armature is returned to its normal closing positon from the opening position by the action of the spring. In such an injection apparatus, however, in order to make high the closing response of the electrically operated injection apparatus, the spring force should be set at a large value especially for the returning action. On the other hand, when the spring force is made large, the opening operation requires a long period of time because of the large spring force acting against the opening force. Thus in order to shorten the time for the valve-opening action, it is necessary that the magnetizing current flowing into the magnetizing current flowing into the magnetic coil is large. Since there are various difficult problems in that a great deal of the magnetizing current must be turned off in a very short period of time and a large quantity of magnetic energy stored by a magnetizing current must be discharged in an instant, it has been difficult to realize an injection apparatus having a excellent response.